5.9 Natural System Modifcations
more widely separated by a more or less unsuitable matrix (Stockwell et al. 2003) . Fragmentation afects all natural areas, especially forests, and it poses increasing problems for major freshwater systems (MEA 2005) . Loss of biodiversity can result when natural communities are degraded or fragmented and can lead to populations that are more susceptible to inbreed- ing, genetic erosion, and problematic population trends (Clark et al. 2010) . Furthermore, pre- scribed burning as a management tool is more difcult in fragmented areas due to dif- culty with smoke management and liability issues. Destruction and degradation of habitat are widely cited as the greatest threats to aquatic species in the United States (Angermeier 1995; Warren et al. 1997; Williams et al. 1993) . Physical alter- ations such as channelization and dredging, aquifer depletion, impoundment and dam construction, and fow modifcation have contributed directly to the decline of aquatic species in the South (Walsh et al. 1995; Etnier 1997) . Increases in impervious surfaces, and subse- quently stormwater fows, have caused changes in sediment transport and stream energy, which has led to limitations in the amount of suitable aquatic habitat and streambed material, especially near urban areas. Te Nature Conservancy (TNC 2000; Smith et al. 2002) and NatureServe (TNC and NatureServe 2001) identify altered surface hydrology (i.e., food control and hydroelectric dams, interbasin transfers of water, drainage ditches, breached levees, artifcial levees, dredged inlets and river channels) and a receding water table as among the most signifcant sources of biological and ecological stress, especially in the Coastal Plain. Habitat fragmentation limits movement and gene fow of area-sensitive species and can isolate species with small home ranges, which makes populations more vulnerable to disturbance, disease, disruption to gene fow between populations, and depredation. Increased amounts of road surfaces and transportation-related projects have impacted populations and natural communities in ecologically sensitive areas. Roads can separate breeding locations and provide substantial barriers to seasonal animal migration path- ways. Increased human development associated with transportation development also brings an increased risk of the introduction of exotic species. Fragmentation disrupts dispersal of many species, especially those that migrate between wet lowlands and dry uplands, and can negatively afect population dynamics and reproductive success. Fragmentation infuences evolution by changing, among other things, the costs and ben- efts of dispersal (Stockwell et al. 2003) . A decrease in population dispersal and population size can lead to a reduction in the efective population size followed by increased genetic drift, reduced genetic variation and increased inbreeding, and a decrease in the time to extinc- tion (Marsack and Swanson 2009; Andersen et al . 2004) . Inbreeding contributes to genetic mutations that decrease disease resistance and the ability of a population to adapt (Lacy 1993) .
While most birds can rapidly fnd and colonize early successional habitat patches, some bird species (grassland birds in particular) are area sensitive and will not use small
707
2015 NC Wildlife Action Plan
Made with FlippingBook - professional solution for displaying marketing and sales documents online